The invention relates to an apparatus for the electrical pretreatment of foils to increase the surface tension of the foil using a roller electrode as a first electrode over which the foil is passed, and a knife electrode as the second electrode. The knife electrode is positioned across the foil at right angles to the direction of foil movement, and spaced from the foil to form an air gap in between the knife electrode and the foil.
Many constructions of this type of apparatus are known. The single knife or blade electrode can be replaced by a cross-sectionally U-shaped knife or blade electrode, so that two discharge edges are available, which are parallel to one another and at right angles to the direction of movement of the foil.